Well, Ezra found a cross guard saber on Malachor but he only found one that we know of. As for Exar Kun, he is now canon. See the visual book for Solo. An item of Vos' is made of black obsidian taken from the temple of the Sith lord Exar Kun. So now Darth Bane and Exar Kun, two well known Sith Lords of Legends, are now canon. I'd like to see a Dark Saber hilt too. If you want something similar to the blade (similar, not exact copy) try the Dark Honor Guard saber with a white black crystal and lightning tuning.